Extrusion die

ABSTRACT

A process for manufacturing an expanded cereal with the overall shape of an array of touching balls and an extrusion die and an extruder for use with the process. The die includes a feed ring for receiving material from an extruder, a cylindrical distribution chamber having a front wall and rear wall which includes the feed ring, and an array of parallel extrusion tubes provided in the front wall of the distribution chamber. The feed ring is in communication with the array of parallel extrusion tubes through the distribution chamber. The distribution chamber also includes a cylindrical distribution insert that extends axially from the center of the feed ring towards the front wall but spaced from the array of extrusion tubes. The process involves cooking and extruding a mixture of starchy material, sugar, oil, and water in a cooker-extruder and forcing the cooked material through the extrusion die.

CROSS REFERENCE TO RELATED APPLICATION

[0001] This application is a division of U.S. application Ser. No.09/559,544, filed Apr. 28, 2000, the content of which is expresslyincorporated herein by reference thereto.

FIELD OF THE INVENTION

[0002] The present invention is directed to an extrusion die, anextruder comprising the extrusion die, a method for manufacturing anexpanded cereal using the extrusion die, and an expanded cereal that isobtained by extrusion through the die.

BACKGROUND

[0003] EP 0,898,890 describes an extrusion die for producing a productthat has the overall shape of a nucleus surrounded by a ring. Theproduct is obtained by extruding a single substance through a die havinga feed orifice plate that opens into an extrusion chamber that isdivided into two concentric chambers by a separating cone. The positionof the cone can be adjusted relative to the outer casing of the die.This adjusts the relative size of the extrusion openings and hence thesize of the nucleus and outer ring.

[0004] U.S. Pat. No. 2,858,218 describes a cereal in the form of flakeswhich has a relief comparable to the surface of a raspberry, and amethod for obtaining such a cereal. The method involves cooking amixture of cereal and water at atmospheric pressure, extruding theresulting cooked paste, using a piston to drive the cooked paste througha die having a number of holes to form parallel filaments of the cookedpaste, combining the filaments, laterally compressing the bundle in atubular extension of the die so that filaments stick together and form acylinder, drying the cylinder, cutting the cylinder transversely intothin slices, and causing the slices to swell under the action of heat.

[0005] U.S. Pat. No. 3,482,992 describes a cereal in the form of flakesmade up of touching pieces, the intersection where the pieces meet beingcolored, and a method for obtaining such a cereal. The method involvescooking a mixture of cereal and water in a cooking device to provide acooked paste; extruding the cooked paste through a die which has anumber of circular outlet orifices, in particular six holes arranged ina circle around a central hole; and injecting a colorant through smallintermediate holes to form parallel strands of cooked paste which arecolored at their interface. The strands are combined into a bundle andcompressed laterally in a tubular extension of the die so that theystick together and form a composite strand. The diameter of the strandis then reduced by drawing it longitudinally and the strand is cuttransversely into thin slices. The slices are dried and made to swellunder the action of heat.

[0006] The object of the present invention is to provide an extrusiondie that makes it possible to produce an expanded cereal with aparticularly attractive three-dimensional shape, the three-dimensionalshape being an array of touching balls.

SUMMARY OF THE INVENTION

[0007] The present invention relates to an extrusion die to prepare anexpanded cereal. The extrusion die includes a feed ring for receivingmaterial from an extuder; a cylindrical distribution chamber having afront wall and a rear wall that includes the feed ring; an array ofparallel extrusion tubes provided in a front wall of the distributionchamber, wherein the array of parallel extrusion tubes is incommunication with the feed ring through the distribution chamber; and acylindrical distribution insert that extends axially from the center ofthe feed ring towards the front wall but is spaced from the array oftubes.

[0008] The array of parallel extrusion tubes may include between about12 to 30 tubes. The tubes of the array may have a cross sectional shapethat is one or more of a circle, oval, polygon, triangle, square,rectangle, or trapezoid. The tubes may be aligned along one or more axesor curves when viewed in cross section. The dimensions of the crosssection of each tube may be between about 1 and 4 mm and the area of thecross section of each tube may be between about 1 and 16 mm². Thedistance between two adjacent tubes in the array may be between about0.2 and 0.6 mm. The array of parallel extrusion tubes may be in twogroups with parallel intersecting axes.

[0009] The invention also relates to an extruder that includes anelongated barrel, one or two processing screws within the elongatedbarrel, at least one extrusion die as described above, and a cuttingmeans.

[0010] In one embodiment the extruder has more than one die. In thisembodiment the barrel has an upstream end and a downstream end, whereinthe downstream end of the barrel is secured to a front plate providedwith an orifice that is in communication with the barrel, the frontplate is attached to a second plate having an opening that is incommunication with the orifice of the front plate, and a bell-shapedpre-distribution chamber, wherein the bell shaped distribution chamberis attached to the second plate and is in communication with the openingof the second plate and is in communication with the feed rings of theextrusion die; and the cutting means is a rotary cutter that rotatesagainst the outlet orifices of the extrusion tubes.

[0011] The invention also relates to a method of manufacturing anexpanded cereal with the overall shape of an array of touching balls.The method involves the steps of providing a cooker-extruder having anelongated barrel with one or two processing screws within the elongatedbarrel with a mixture of between about 60 and 90 parts by weight of astarchy material, up to 15 parts by weight of sugar, up to 10 parts byweight of oil, and a sufficient amount of water so that the mixture hasa water content of between about 15 and 25 percent by weight; cookingthe mixture under positive pressure in the cooker-extruder to provide athermoplastic substance; extruding the thermoplastic substance throughat least one die having an array of parallel extrusion tubes each havingan outlet orifice so that the thermoplastic substance expands when itexits the outlet orifices of the extrusion tubes to provide a bundle ofstrands of expanded thermoplastic substance that stick together; andcutting the bundle into slices as they exit from the outlet orifices ofthe extrusion tubes to provide an expanded cereal.

[0012] The cooking may be conducted at a temperature of between about105° C. and 180° C., a pressure of between about 40 and 180 bar, arotation speed for the one or more screws of between about 240 and 370rpm, and wherein the ratio of the length of the screw to the diameter ofthe screw is between about 9 and 24. The coefficient of expansion forthe extruded strands may be between about 2 and 4. The extruded strandsmay have a porous texture. The extruded strands may have a residualwater content of between about 5 and 12 percent and may be further driedto a water content of between about 1 and 3 percent.

[0013] The starchy material may be one or more of a flour selected fromthe group consisting of wheat, barley, rice, and corn flour or a starchselected from the group consisting of wheat, barley, rice, tapioca,potato, and corn starch. The sugar may be one or more of sucrose,glucose, or fructose. The oil may be present in an amount of betweenabout 4 and 10 percent by weight and may be a butter oil or a vegetableoil. The mixture further include up to 1.5 parts of calcium that may beprovided by calcium carbonate or calcium triphosphate or one or morevitamins, trace elements, sodium chloride colorings, or flavorings.

[0014] The invention further relates to an expanded cereal prepared bythe method of the invention. The expanded cereal product may be coatedwith one or more of a chocolate coating, a sugar syrup, a fruit syrup, ahoney syrup, or a coating that contains one or more vitamins orflavorings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is an axial view of one embodiment of the die of theinvention;

[0016]FIG. 2 is a cross section view of the die depicted in FIG. 1,

[0017]FIG. 3 is a partial cross section view of one embodiment of anextruder comprising a number of dies;

[0018]FIG. 4 is a face view of the extruder depicted in FIG. 3; and

[0019]FIG. 5 is a photograph showing one embodiment of the cereal fromthree different angles.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] The extrusion die of the invention is depicted in FIG. 1. Theextrusion die comprises a feed ring 1 that forms the rear wall of acylindrical distribution chamber 2 and opens into the cylindricaldistribution chamber 2. The cylindrical distribution chamber 2communicates with an array of parallel extrusion tubes 3 provided in afront wall 4 of the cylindrical distribution chamber 2. A cylindricaldistribution insert 5 extends axially from the center of the feed ring 1towards the front wall but is spaced from the front wall. Preferably,the space between the cylindrical distribution insert 5 and the frontwall is between about 1 and 5 mm.

[0021] The feed ring 1 may be, for example in the form of two concentricannuli 11 and 12 connected by juxtaposed tubular hoops 13. The number oftubular hoops may vary from between about 4 and 20, preferably betweenabout 5 and 12.

[0022] The cylindrical distribution insert 5 has a first cylindricalupstream part 16 and a second frustoconical downstream part 17. Thecylindrical distribution insert 5 evens out the rate of displacementacross the width of the extrusion front when a thermoplastic material isextruded through the cylindrical distribution chamber. The cylindricaldistribution insert 5 assures that the flow of material through thearray of tubes is distributed homogeneously in front of the array. Byhomogeneously is meant there are no preferential paths for the materialbeing extruded to follow and that the flow of material has substantiallythe same speed in front of each individual tube of the array. The widthof the extrusion front corresponds to the width or diameter of the arrayof parallel extrusion tubes.

[0023] The array of extrusion tubes 3 is an array of several individualcylindrical parallel tubes. The array may comprise from about 2 to 40tubes, preferably from about 12 to 30 tubes. The individual tubes of thearray may have cross sections in a variety of shapes including, but notlimited to a, circle, oval, polygon, triangle, square, rectangle, andtrapezoid. The shape and size of the cross section of the individualtubes in any given array may be the same or different. Preferably, thetubes are arranged so that they are aligned along a number of axes orcurves when viewed in cross section. The tubes, however, may also bearranged randomly and in no particular order. The cross section of thetubes may have dimensions, i.e., diameters, lengths, or widths ofbetween about 1 and 4 mm. Preferably, the cross section of the tubes hasa surface area or aperture of between about 1 and 16 mm². Preferably,the tubes are relatively close together. The distance between two tubesof the array may be from about 0.2 to 0.6 mm. In a preferred embodiment24 cylindrical tubes each having the same circular cross section arearranged in two groups with parallel axes intersecting at angles asdepicted in FIG. 4.

[0024] The extruder of the invention comprises an elongated barrelcontaining one or two processing screws, at least one extrusion die ofthe invention, and a cutting means.

[0025] The phrase “processing screw” means an extrusion screw rotatinginside the bore of a barrel or two extrusion screws rotating inside oftwo secant bores of a barrel. The screws have processing members such asflights helically wound about their axis. The configuration, pitch,depth, and hand of the flights may be configured in various ways alongthe axis of the screw so as to define zones for various processingoperations such as conveying, wetting, mixing, shearing, compressing,and/or cooking. The processing screws may be made as a single piece orby assembling various processing members by successively slipping theprocessing members onto a spindle.

[0026] The cutting means cuts the extrudate as it emerges from theoutlet orifices of the extrusion tubes. Preferably, the cutting means isa rotary cutter 14 that rotates against the outlet orifices of theextrusion tubes 3 of the array, i.e., against the front wall of the die.The rotating cutter may have one blade or a number of blades, preferablythe rotating cutter has between about 2 and 4 blades.

[0027] The extruder may include several extrusion dies such as thosedepicted in FIGS. 1 and 2. FIGS. 3 and 4, depict an embodiment of theinvention wherein the extruder comprises a number of extrusion dies. InFIG. 3 the downstream end of the elongated extrusion barrel ends at afront plate 7 that is provided with an orifice 8 that is incommunication with the barrel. The front plate 7 is attached to a secondplate 15 having an opening 10 that is in communication with the opening8 in the front plate 7 and is in communication with a bell shapedpre-distribution chamber 9. The pre-distribution chamber 9 communicateswith the distribution chambers 2 of the dies via the feed rings 1.Preferably, the extruder has between about 2 and 30 dies.

[0028] By downstream end of the extruder is meant the end of theextruder closest to the extrusion die. By upstream end of the extruderis meant the end of the extruder most distant from to the extrusion die.The overall flow of material in the extruder is from the upstream endtowards the downstream end.

[0029] When the extruder has several dies, the number of dies that canbe used can be adjusted according to the output of the extruder. Forexample, one die in two or one die in three can be closed by blockingthe dies feed ring 1 with a cover. The cover is fixed to the dies centerand replaces the distribution insert 5. FIG. 3 depicts an extruderwherein the lower die is blocked by replacing the distribution insert 5with a cover 15 to block the feed ring 1 of the die.

[0030] The extruder of the invention can be used to prepare a cerealthat has the overall shape of an array of touching balls. The touchingballs of the array may be of similar or different shapes, preferablythey are round and/or elongated. The touching balls may be aligned ormay not be aligned along an axes or a curve. The array may have anoverall thickness of between about 4 and 16 mm. The overall shape of thearray may be flat or it may be somewhat curved. A variety of shapes arepossible for the overall periphery of the array. Preferably the shape ofthe periphery of the array is square, rectangular, circular, or oval,modulated by the bumps formed by the balls located at the edges.

[0031] The cereal of the invention may be used to manufacture a varietyof products such as, for example, breakfast cereals, crunchy pet food,and the like.

[0032] When the cereal of the invention is a breakfast cereal it can beeaten as it is or it may be coated. Suitable coatings for use with thecereal of the invention include, but are not limited to, a chocolatecoating, a sugar syrup, a fruit syrup, a honey syrup, and a coatingcontaining vitamins and flavorings.

[0033]FIG. 5 depicts one embodiment of the cereal that can be obtainedby extrusion through a die similar to those depicted in FIGS. 1 and 4.

[0034] In this embodiment, the cereal has the overall shape of an arrayof touching balls of the same round shape and of the same dimensionsaligned in two groups with parallel axes intersecting at angles. Thearray of balls has a periphery of overall rectangular shape but isslightly curved on one side (the side where the cutter detached thecereal from the composite strand leaving the die).

[0035] The cereal, having the overall shape of an array of touchingballs, is prepared by forming a mixture comprising between about 60 and90 parts by weight of a starchy material, up to about 15 parts by weightof sugar, and up to about 10 parts by weight of oil, and addingsufficient water to provide a water content of between about 15 to 25percent by weight. The resulting mixture is then cooked, extruded, andexpanded at a pressure of between about 40 to 180 bar and a temperaturebetween about 105° C. and 180° C. The mixture is extruded through atleast one die comprising an array of parallel extrusion tubes so as toobtain a bundle of strands of expanded thermoplastic substance thatstick together. The bundle is then cut into slices at the outletorifices of the extrusion tubes.

[0036] The starchy material may be a cereal flour including, but notlimited to, one or more of wheat, barley, rice, or corn flour. Thestarch material may also be a starch including, but not limited to, oneor more of wheat, barley, rice, tapioca, potato, or corn starch.

[0037] Any sugar suitable for manufacturing cereal may be used accordingto the method of the invention. For example, the sugar may be sucrose,glucose or fructose.

[0038] The oil is preferably added in the proportion of between about 4and 10 parts by weight. Oils that may be used in the method of theinvention include, but are not limited to, butter oil and vegetable oilssuch as palm nut oil.

[0039] The mixture may further contain up to 1.5 parts of calcium, forexample, in the form of calcium carbonate or calcium triphosphate.

[0040] The mixture may further include other additives including, butnot limited to, vitamins, trace elements, sodium chloride, colorings,and artificial or natural flavorings such as cocoa. For example, up to 6parts of cocoa may be added.

[0041] The cooking and extrusion may be performed in a cooker-extruderhaving a screw with a length to diameter ratio of between about 9 and24, with the screws rotating at between about 240 and 370 rpm, at apressure in the range of about 40 and 180 bar, and at a temperature inthe range of about 105° C. to 180° C. The cooked and extruded mixtureexpands as it exits the cooker-extruder due to the decrease in pressure.Preferably the extruded strands exhibit an expansion coefficient for theextruded strands of between about 2 and 4. By “expansion coefficient” ismeant the increase in volume of the mixture after it exits the dierelative to the volume of the mixture before it goes through the die.

[0042] Water escapes from the thermoplastic mass in the form of steamduring expansion so that the extruded strands have a porous texture. Theresidual water content of the extruded strands is preferably betweenabout 5 and 12 percent.

[0043] The resulting expanded cereal may be further dried. Preferably,the cereal is dried by passing it continuously through a hot air ovenuntil the residual water content is reduced to between about 1 to 3percent.

EXAMPLES

[0044] The invention is further defined by reference to the followingexamples describing in detail the production of a preferred form of thecereal of the invention, an expanded breakfast cereal. The example isrepresentative, and should not be construed to limit the scope of theinvention in any way.

[0045] The cereal is prepared by cooking and extruding a mixture basedon flour and water in a cooker-extruder comprising several diesaccording to the invention. In the following example, as in the entiretyof this description, parts and percentages are given by weight.

[0046] A twin-screw cooker-extruder comprising several dies similar tothe one illustrated in FIGS. 3 and 4 was used to produce expandedcereals with the shape of an array of touching round balls asillustrated in FIG. 5.

[0047] A mixture with the following composition was prepared (in parts,except for the added water): Rice flour 40 Cornflour 12 Wheat flour 22Sucrose 10 Palm nut oil 5 Salt/spices 3

[0048] Water (added to a water content of 18 percent)

[0049] The dry powders were first mixed and the resulting dry mixture,the oil, and the water added to a CLEXTRAL type BC-72 twin-screwextruder equipped with a screw having a diameter of 88 mm and a lengthof 900 mm. The resulting mixture was mixed in the extruder.

[0050] The mixture was then cooked and extruded at a temperature ofabout 170° C. and a pressure of between about 100 and 120 bar, with theextruder screws rotating at 310 rpm.

[0051] The resulting thermoplastic mass was extruded through 6 arrays of24 extrusion tubes, the extrusion tubes having a diameter of 1.3 mm andthe distance between two tubes being 0.3 mm.

[0052] The thermoplastic mass was extruded into the ambient space andimmediately cut into slices using a four-bladed cutter rotating againstthe front wall of the dies at a speed of 800 rpm.

[0053] The resulting cereal had the overall shape of an array of 24touching balls with the same round shape and the same dimensions andaligned in two groups having parallel axes that intersect at angles. Thearray of balls had a periphery with an overall rectangular shape thatwas slightly curved on the side where the cutter detached the cerealfrom the composite strand leaving the die.

[0054] The cereal had a thickness of about 6 mm, a width of about 15 mm,and a length of about 20 mm.

What is claimed is:
 1. An extrusion die comprising a feed ring forreceiving material from an extruder; a cylindrical distribution chamberhaving a front wall and a rear wall that includes the feed ring; anarray of parallel extrusion tubes provided in a front wall of thedistribution chamber, wherein the array of parallel extrusion tubes isin communication with the feed ring through the distribution chamber;and a cylindrical distribution insert that extends axially from thecenter of the feed ring towards the front wall but is spaced from thearray of tubes.
 2. The extrusion die of claim 1 , wherein the array ofparallel extrusion tubes comprises between about 12 to 30 tubes.
 3. Theextrusion die of claim 1 , wherein the tubes of the array have a crosssectional shapes comprising one or more of a circle, oval, polygon,triangle, square, rectangle, or trapezoid.
 4. The extrusion die of claim1 , wherein the tubes are aligned along one or more axes or curves whenviewed in cross section.
 5. The extrusion die of claim 1 , wherein thedimensions of the cross section of each tube is between about 1 and 4mm.
 6. The extrusion die of claim 1 , wherein the area of the crosssection of each tube is between about 1 and 16 mm².
 7. The extrusion dieof claim 1 , wherein the distance between two adjacent tubes in thearray is between about 0.2 and 0.6 mm.
 8. The extrusion die of claim 1 ,wherein the array of parallel extrusion tubes is in two groups withparallel intersecting axes.
 9. An extruder comprising an elongatedbarrel, one or two processing screws within the elongated barrel, atleast one extrusion die according to claim 1 , and a cutting means. 10.The extruder of claim 9 , comprising more than one die; wherein thebarrel has an upstream end and a downstream end, wherein the downstreamend of the barrel is secured to a front plate provided with an orificethat is in communication with the barrel, the front plate is attached toa second plate having an opening that is in communication with theorifice of the front plate, and a bell-shaped pre-distribution chamber,wherein the bell-shaped pre-distribution chamber is attached to thesecond plate and is in communication with the opening of the secondplate and is in communication with the feed rings of the extrusion die;and wherein the cutting means is a rotary cutter that rotates againstthe outlet orifices of the extrusion tubes.